Probably the last update...things are working well.

I just wanted to cap off this Build Log with some final notes.

Since my last post I have:
1. Installed a Greg Wades extruder and modified it for a bowden tube.
2. Eliminated the MKV-BV J-Head. Replaced with Ebay 3 Piece hot end ($17).
3. Moved to Shaxon black ABS, 1.75mm.
4. Lowered my Z lift accelerations.
5. Installed a 30mm hot end fan with a shroud.

As it stands the printer is running at 30mm/s with almost perfect print quality. Only very slight spider webs.

In hindsight it's easy for me to recognize that I was trying to extrude my MG Chemicals silver ABS at too high of a temperature. Once I switched to the Shaxon black ABS and started experiencing cold extrusions it was obvious. Layer adhesion was the giveway. The Shaxon was struggling with layer adherence and the MG Chem was sticking fine, but oozing all over. Also, the 3 piece hot end really helped with oozing and heat creep jamming.

What really surprises me is the fairly large difference in temperature requirements for the "same" type of plastic. I'm sure I could have dropped down to 215c with the MG Chem silver ABS and been fine, but the Shaxon black ABS needs more like 245c!

The huge discrepancy in glass transition temperature could be physically felt in the filament. The Shaxon black ABS filament is noticeably stiffer than the MG Chemicals silver ABS filament. Also, the low glass transition temperature of the MG Chemicals ABS was causing it to bend/break at the extruder with high ambient temperatures (95f in my apartment sometimes), and only made the heat creep jamming worse if I wasn't standing there monitoring it when it broke.

Anyway, if I had to pass off any advice from my experiences it would be:
- Get the feel of what it's like to hand feed filament through a "clean" extruder. This well help you diagnose when your extruder is clogged or jammed.
- Start at 230c and then go down by 5c until you start seeing minimal oozing once you stop extruding. It's good to have a little. Then move back up by 5c to find the sweet spot for layer adhesion.
- Don't try to print in high ambient temperatures.
- Extruder E-Step calibration is an art, and is not always 1:1. If someone can argue otherwise...please speak up.